Guests message on game pages when logged out?

I was playing Roblox when I was randomly logged out. But, it didn't kick me immediately back to the sign-in screen. I try to play a game and it says this gem: Guests cannot join this experience

I don't know whether this is just an old relic that managed to stay (and if it is, please roblox, if you're reading this, DON'T REMOVE THIS LIKE THAT OTHER THING), or if it is actually something to do with guests.